1. Field of the Invention
The present invention relates to a support structure for supporting processing objects, such as semiconductor wafers, and to a processing apparatus.
2. Description of the Related Art
In the manufacturing of a semiconductor integrated circuit, a semiconductor wafer, e.g. comprised of a silicon substrate, is generally subjected to various types of processing, such as film-forming processing, etching, oxidation, diffusion processing, modification, removal of a natural oxide film, etc. Such processing is carried out by using a single-wafer processing apparatus which processes wafers in a one-by-one manner, or a batch processing apparatus which processes a plurality of wafers at a time. When processing of a semiconductor wafer is carried out, for example, by using a vertical batch processing apparatus as disclosed, for example, in Japanese Patent Laid-Open Publication No. H6-275608, semiconductor wafers are first transferred from a cassette, which can house a plurality of, e.g. about 25, wafers, to a vertical wafer boat where the wafers are supported in multiple stages.
The wafer boat can generally hold about 30 to 150 wafers, depending on the wafer size. After the wafer boat, housing wafers therein, is loaded into an evacuable processing container from below, the interior of the processing container is kept airtight. A predetermined heat treatment of the wafers is then carried out while controlling processing conditions, such as the flow rate of a processing gas, the processing pressure, the processing temperature, etc. Taking film-forming processing as an example of heat treatment, known film-forming methods include CVD (chemical vapor deposition) (Japanese Patent Laid-Open Publication No. 2004-006551) and ALD (atomic layer deposition).
For the purpose of improving the characteristics of circuit elements, a demand exists for reducing heat history in the process of manufacturing a semiconductor integrated circuit. An ALD method, which involves intermittently supplying a raw material gas, etc. so as to repeatedly form one layer to a few layers of a film at the atomic or molecular level and which is capable of performing intended processing without exposing wafers to excessively high temperatures, is therefore becoming more frequently used (Japanese Patent Laid-Open Publications Nos. H6-45256 and H11-87341).